// ptr_ops.c -- pointer operations
#include <stdio.h>

int main(void)
{
	int urn[5] = {100,200,300,400,500};
	int * ptr1, * ptr2, * ptr3;
	
	ptr1 = urn;			//assign an address to a pointer
	ptr2 = &urn[2];		//ditto
						//dereference a pointer and take
						//the address of a pointer
	printf("pointer value, dereferenced pointer, pointer address:\n");
	printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n",
			ptr1, *ptr1, &ptr1);
	//pointer addition
	ptr3 = ptr1 + 4;
	printf("\nadding an int to a pointer:\n");
	printf("ptr1 + 4 = %p, *(ptr1 + 3) = %d\n",
			ptr1 + 4,*(ptr1 + 3));
	ptr1++;				//increment a pointer
	printf("\nvalues after ptr1++:\n");
	printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n",
			ptr1, *ptr1, &ptr1);
	ptr2--;				//decrement a pointer
	printf("\nvalues after --ptr2:\n");
	printf("ptr2 = %p, *ptr2 = %d, &ptr2 = %p\n",
			ptr2, *ptr2, &ptr2);
	--ptr1;				//restore to original value
	++ptr2;				//restore to original value
	printf("\nPointer reset to orginal values:\n");
	printf("ptr1 = %p, ptr2 = %p\n", ptr1, ptr2);
						//subtract one pointer from another
	printf("\nsubtracting one pointer from another:\n");
	printf("ptr2 = %p, ptr1 = %p, ptr2 - ptr1 = %d\n",
			ptr2, ptr1, ptr2 - ptr1);
						//subtract an integer from a pointer
	printf("\nsubtracting an int from a pointer:\n");
	printf("ptr3 = %p, ptr3 - 2 = %p\n",
			ptr3, ptr3 - 2);
	return 0;
}